Clutch control reference value setting method

ABSTRACT

A method of setting a clutch control reference value may make it possible to more accurately learn the VKP of a hydraulic multi-plate clutch controlled by a solenoid valve, improving the accuracy of clutch control, and furthermore, to improve the quality of shifting a vehicle by the precise control of a transmission provided with such a clutch.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No.10-2021-0030996, filed Mar. 9, 2021, the entire contents of which isincorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a technology for setting a controlreference value for controlling a hydraulic multi-plate clutch used in atransmission or the like of a vehicle.

Description of Related Art

As illustrated in FIG. 1, a hydraulic multi-plate clutch, a plurality ofclutch plates 500, and a plurality of clutch disks 502 alternatelyoverlap each other between two rotation bodies A and B, and a piston 504which is moved by hydraulic pressure pressurizes the overlapped clutchplates 500 and clutch disks 502 to be in close contact with each other,forming an engagement state in which power is transmitted. When thehydraulic pressure acting on the piston 504 is released, the elasticforce of a spring 506 causes the piston 504 to return to the originalposition thereof, forming a released state in which the clutch plates500 and the clutch disks 502 are capable of rotating relative to eachother.

For reference, hereinafter, the hydraulic multi-plate clutch will besimply referred to as a “clutch”.

In FIG. 1, two clutches are configured, and each clutch is configured tobe supplied with a hydraulic pressure in a controlled manner. A solenoidvalve 510 controlled by a controller 508 adjusts a supplied linepressure such that a desired hydraulic pressure may be supplied to thepiston 504 of the clutch. The hydraulic pressure supplied to the piston504 may be measured by each hydraulic sensor 512.

The hydraulic pressure supplied to the clutch through the control of thesolenoid valve 510 tends to be linearly proportional to the controlcurrent applied to the solenoid valve 510 by the controller 508, exceptfor some sections.

The reason why the control current and hydraulic pressure are not linearin some sections is mainly due to the structure of the clutch and theoperation process obtained therefrom.

First, referring to the operation process of the clutch, when thecontrol current of the solenoid valve 510 is gradually increased, thespring 506 of the clutch is initially maintained without beingcompressed. Accordingly, as the spring 506 is compressed due to theincrease of the control current, the piston 504 starts to move.

The movement of the piston 504 is performed to a point where the clutchplate 500 and the clutch disk 502 are pressed and a substantialfrictional force starts to be generated between the clutch plate 500 andthe clutch disk 502. Thereafter, the pressure between the clutch plate500 and the clutch disk 502 is increased with the hydraulic pressureincreased due to the increase of the control current. However, it may beseen that the amount of movement of the piston 504 is insignificant andthe piston 504 hardly moves.

As described above, in the operation process of the clutch according tothe increase of the control current, in the initial stage in which thespring 506 of the clutch is not compressed, the hydraulic pressureacting on the piston 504 of the clutch starts to increase linearly withthe increase of the control current. However, as the piston 504 movesdue to the increase of the hydraulic pressure, the spring 506 starts tobe compressed. Accordingly, until the piston 504 is in the state ofbeing substantially unable to move due to close contact between theclutch plates 500 and the clutch disks 502, the volume of the space inwhich the hydraulic pressure of the clutch acts is changed, whichresults in a section in which the hydraulic pressure is nonlinear.

That is, some sections in which the control current and hydraulicpressure are not linear occur in the present way.

Thereafter, the piston 504 increases the pressure applied to the clutchplate 500 and the clutch disk 502, but when the amount of movementbecomes insignificant, the hydraulic pressure of the clutch due to theincrease of the control current increases linearly again.

The transmission of power between the two rotation bodies connected bythe clutch is substantially performed from a position at which thehydraulic pressure recovers linearity again since the movement of thepiston 504 is substantially stopped due to close contact between theclutch plates 500 and the clutch disks 502, and thus the change in thevolume of the space in which the hydraulic pressure of the clutch actsis terminated. Thus, the present position is defined as a “volumetrickiss point (VKP)” or a “volumetric touch point (VTP)”, and whencontrolling the clutch, the solenoid valve 510 is controlled bybasically considering the VKP as a control reference value.

Therefore, it is desirable to enable the controller 508 to learn and setthe VKP as rapidly and accurately as possible during the manufacture ofa transmission, and to enable the controller to control the clutch basedon the correct VKP set as described above in the state in which thetransmission is mounted on a vehicle thereafter.

The information included in Background of the present invention sectionis only for enhancement of understanding of the general background ofthe present invention and may not be taken as an acknowledgement or anyform of suggestion that this information forms the prior art alreadyknown to a person skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing amethod of setting a clutch control reference value that makes itpossible to more accurately learn the VKP of a hydraulic multi-plateclutch controlled by a solenoid valve, improving the accuracy of clutchcontrol, and furthermore, to improve the quality of shifting a vehicleby the precise control of a transmission provided with such a clutch.

In view of the foregoing, a method of setting a clutch control referencevalue according to various exemplary embodiments of the presentinvention includes: generating, by a controller, a current-hydraulicmodel using a slope of a measured hydraulic pressure obtained bymeasuring a hydraulic pressure acting on a clutch while changing acurrent applied by the controller to a solenoid valve electricallyconnected to the controller and fluidically connected to the clutch;setting, by the controller, a current at which a difference between amodel hydraulic pressure determined according to the current-hydraulicpressure model and the measured hydraulic pressure is maximum as atemporary VKP while changing the current applied to the solenoid valve,and accumulating, by the controller, a number of times of setting thetemporary VKP; determining, by the controller, whether a predeterminedpressure drop occurs in a state in which the solenoid valve is made toform a pressure obtained by adding a predetermined first referencepressure to the temporary VKP; determining, by the controller, whetherthe predetermined pressure drop occurs in a state in which the solenoidvalve is made to form a pressure obtained by subtracting a predeterminedsecond reference pressure from the temporary VKP; making, by thecontroller, the solenoid valve form a fourth reference pressure obtainedby subtracting a predetermined third reference pressure from thetemporary VKP when the pressure drop does not occur in the state inwhich the solenoid valve is made to form the pressure obtained by addingthe predetermined first reference pressure to the temporary VKP and whenthe pressure drop occurs in the state in which the solenoid valve ismade to form the pressure obtained by subtracting the predeterminedsecond reference pressure from the temporary VKP; determining, by thecontroller, the pressure drop in a state in which the solenoid valveforms the fourth reference pressure and determining, by the controller,whether the pressure drop is within a predetermined reference range;storing, by the controller, the fourth reference pressure as a candidateVKP upon determining that the pressure drop is within the predeterminedreference range, and accumulating, by the controller, a number of timesof storing the same fourth reference pressure as the candidate VKP; anddetermining, by the controller, whether the pressure drop is within thepredetermined reference range and repeating, by the controller, thestoring of the fourth reference pressure as the candidate VKP and thesetting of the candidate VKP as a final VKP upon determining that thenumber of times of storing the same fourth reference pressure as thecandidate VKP becomes a predetermined first reference number of times.

When the pressure drop occurs in the state in which the solenoid valveis made to form the pressure obtained by adding the predetermined firstreference pressure to the temporary VKP or upon determining that thepressure drop does not occur in the state in which the solenoid valve ismade to form the pressure obtained by subtracting the predeterminedsecond reference pressure from the temporary VKP, the setting of thetemporary VKP and the accumulating of the number of times of setting thetemporary VKP may be repeated.

The setting of the temporary VKP and the accumulating of the number oftimes of setting the temporary VKP may be repeated together with thegenerating of the current-hydraulic pressure model.

When the number of times of setting the temporary VKP is a predeterminedfirst reference number, among temporary VKPs that have been set untilthe first reference number is reached, an average value of remainingtemporary VKPs excluding the maximum value and the minimum value may beset as the final VKP.

The method may further include updating the fourth reference pressure asa pressure obtained by subtracting a predetermined fifth referencepressure from the fourth reference pressure upon determining that thepressure drop is smaller than the reference range as a result ofdetermining the pressure drop in the state in which the solenoid valveis set the fourth reference pressure, wherein the determining of thepressure drop may be repeated in a state in which the solenoid valve ismade to form the updated fourth reference pressure.

The method may further include updating the fourth reference pressure asa pressure obtained by adding a predetermined sixth reference pressureto the fourth reference pressure upon determining that the pressure dropis greater than the reference range as a result of determining thepressure drop in the state in which the solenoid valve is set the fourthreference pressure, wherein the determining of the pressure drop may berepeated in a state in which the solenoid valve is made to form theupdated fourth reference pressure.

The present invention makes it possible to more accurately learn the VKPof a hydraulic multi-plate clutch controlled by a solenoid valve,improving the accuracy of clutch control, and furthermore, to improvethe quality of shifting a vehicle by the precise control of atransmission provided with such a clutch.

The methods and apparatuses of the present invention have other featuresand advantages which will be apparent from or are set forth in moredetail in the accompanying drawings, which are incorporated herein, andthe following Detailed Description, which together serve to explaincertain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a control circuit of a hydraulicmulti-plate clutch to which various exemplary embodiments of the presentinvention is applicable;

FIG. 2 and FIG. 3 are flowcharts each illustrating an exemplaryembodiment of a method of setting a clutch control reference valueaccording to various exemplary embodiments of the present invention;

FIG. 4 is a graph illustrating how a controller acquires a slope of ameasured hydraulic pressure while increasing current applied to asolenoid valve;

FIG. 5 is a graph illustrating how a controller sets a temporary VKPwhile increasing current applied to a solenoid valve;

FIG. 6 is a graph illustrating a situation in which a pressure drop doesnot occur since no sticking occurs in the solenoid valve; and

FIG. 7 is a graph illustrating a situation in which a pressure dropoccurs due to sticking occurring in a solenoid valve.

It may be understood that the appended drawings are not necessarily toscale, presenting a somewhat simplified representation of variousfeatures illustrative of the basic principles of the present invention.The specific design features of the present invention as includedherein, including, for example, specific dimensions, orientations,locations, and shapes will be determined in part by the particularlyintended application and use environment.

In the figures, reference numbers refer to the same or equivalent partsof the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of thepresent invention(s), examples of which are illustrated in theaccompanying drawings and described below. While the presentinvention(s) will be described in conjunction with exemplary embodimentsof the present invention, it will be understood that the presentdescription is not intended to limit the present invention(s) to thoseexemplary embodiments. On the other hand, the present invention(s)is/are intended to cover not only the exemplary embodiments of thepresent invention, but also various alternatives, modifications,equivalents and other embodiments, which may be included within thespirit and scope of the present invention as defined by the appendedclaims.

Referring to FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7, anexemplary embodiment of a method of setting a clutch control referencevalue includes: generating, by a controller, a current-hydraulic modelusing a slope of a measured hydraulic pressure obtained by measuring ahydraulic pressure acting on a clutch while changing a current appliedby the controller to a solenoid valve (S10); setting, by the controller,a current at which a difference between a model hydraulic pressuredetermined according to the current-hydraulic pressure model and themeasured hydraulic pressure is maximum as a temporary VKP while changingthe current applied to the solenoid valve, and accumulating a number oftimes of setting the temporary VKP (S20); determining, by thecontroller, whether a predetermined pressure drop occurs in a state inwhich the solenoid valve is made to form a pressure obtained by adding apredetermined first reference pressure to the temporary VKP (S30);determining, by the controller, whether the predetermined pressure dropoccurs in a state in which the solenoid valve is made to form a pressureobtained by subtracting a predetermined second reference pressure fromthe temporary VKP (S40); making, by the controller, the solenoid valveform a fourth reference pressure obtained by subtracting a predeterminedthird reference pressure from the temporary VKP when the pressure dropdoes not occur in the state in which the solenoid valve is made to formthe pressure obtained by adding the predetermined first referencepressure to the temporary VKP and when the pressure drop occurs in thestate in which the solenoid valve is made to form the pressure obtainedby subtracting the predetermined second reference pressure from thetemporary VKP (S50); determining, by the controller, the pressure dropin a state in which the solenoid valve forms the fourth referencepressure and determining, by the controller, whether the pressure dropis within a predetermined reference range (S60); storing, by thecontroller, the fourth reference pressure as a candidate VKP upondetermining that the pressure drop is within the predetermined referencerange, and accumulating, by the controller, the number of times ofstoring the same fourth reference pressure as the candidate VKP (S70);and determining, by the controller, whether the pressure drop is withinthe predetermined reference range and repeating, by the controller, thestoring of the fourth reference pressure as the candidate VKP and thesetting of the candidate VKP as a final VKP upon determining that thenumber of times of storing the same fourth reference pressure as thecandidate VKP becomes a predetermined second reference number of times(S80).

Of course, when the final VKP is set as described above, the controlleris configured for controlling the solenoid valve using the final VKPthereafter, accurately controlling the clutch provided to receive thehydraulic pressure controlled by the solenoid valve. When the clutch isin a transmission mounted on a vehicle, it is possible to ensureexcellent transmission quality of the vehicle through precise control ofthe transmission.

In the operation in which the controller generates a current-hydraulicmodel using the slope of a measured hydraulic pressure obtained bymeasuring the hydraulic pressure acting on the clutch while changing thecurrent applied to the solenoid valve, it is possible to measure thehydraulic pressure acting on the clutch while gradually increasing thecurrent applied to the solenoid valve.

In the instant case, as illustrated in FIG. 4, the slope of the measuredhydraulic pressure is obtained in a section in which the hydraulicpressure increases linearly following a section in which the hydraulicpressure increases nonlinearly and then increases linearly with theincrease in current.

In the setting, as a temporary VKP, the current at which the differencebetween the model hydraulic pressure determined based on thecurrent-hydraulic model and the measured hydraulic pressure is maximumwhile changing the current applied to the solenoid valve the hydraulicpressure acting on the clutch is measured while gradually increasing thecurrent applied to the solenoid valve, and as illustrated in FIG. 5, apoint where the difference between the model hydraulic pressure and themeasured hydraulic pressure is maximized is found, and the current atthat time is set as the temporary VKP.

Furthermore, the temporary VKP, which is set as described above, iscontinuously stored until the number of times of setting the temporaryVKP reaches a first reference number of times to be described later.

The state in which the solenoid valve is made to form a pressureobtained by adding a predetermined first reference pressure to atemporary VKP means the state in which a current obtained by adding acurrent substantially configured for forming the first referencepressure to the current of the temporary VKP is applied to the solenoidvalve.

That is, here, pressures and currents are treated as physical quantitieswhich may be replaced with each other by the current-hydraulic model.

Determining whether a predetermined pressure drop occurs in the state inwhich the solenoid valve is made to form a pressure obtained by adding apredetermined first reference pressure to the temporary VKP meansdetermining the degree to which the measured hydraulic pressure followsthe model hydraulic pressure while additionally increasing the currentafter a time for forming a target pressure has elapsed in the state inwhich the current configured for forming the pressure obtained by addingthe predetermined first reference pressure to the temporary VKP, asillustrated in FIG. 6.

That is, when the current applied to the solenoid valve is additionallyincreased in the state in which the target pressure (the temporaryVKP+the first reference pressure) is formed, if the temporary VKP issubstantially the same as the actual VKP and no sticking occurs in thesolenoid valve, it is necessary for the measured hydraulic pressure toimmediately follow the model hydraulic pressure such that no pressuredrop is caused, as illustrated in FIG. 6. Thus, it is determined whethersuch a behavior occurs.

When sticking occurs in the solenoid valve even if the temporary VKP issubstantially the same as the actual VKP, the model hydraulic pressureimmediately increases as the current increases, but the measuredhydraulic pressure increases after a delay when the stuck state isresolved rather than immediately increasing, as illustrated in FIG. 7.In the instant case, it is possible to determine the pressure drop byintegrating the difference between the model hydraulic pressure and themeasured hydraulic pressure.

That is, it is possible to determine the pressure drop by integratingthe difference between the model hydraulic pressure and the measuredhydraulic pressure when the current is additionally increased from thestate in which the solenoid valve is made to form an arbitrary targetpressure near the actual VKP as described above.

Of course, as can also be seen from FIG. 6 and FIG. 7, a slightdifference is always caused between the model hydraulic pressure and themeasured hydraulic pressure due to a basic response delay even when thesolenoid valve is normal. Thus, the pressure drop obtained byintegrating the difference between the model hydraulic pressure and themeasured hydraulic pressure as described above will always be positive.

Accordingly, when there is a value substantially remaining aftersubtracting the pressure drop according to the basic response delay fromthe pressure drop determined as described above, it is determined thatthe pressure drop occurs.

The first reference pressure is set to a level that makes it possible todetermine whether or not sticking occurs in the solenoid valve asdescribed above, and to determine whether the temporary VKP is locatedclose to the actual VKP. For example, the first reference pressure maybe set to 0.5 bar.

The time for forming the target pressure is set in consideration of asufficient time for the hydraulic pressure to substantially and stablyreach the target pressure after a current to form the target pressure isapplied to the solenoid valve. For example, the time for forming thetarget pressure may be set to 1.3 seconds or the like.

Even in the determining whether the pressure drop occurs in the state inwhich the solenoid valve forms a pressure obtained by subtracting apredetermined second reference pressure from the temporary VKP, it isdetermined whether the pressure drop occurs by observing the followingstate of the measured hydraulic pressure according to the increase ofthe model hydraulic pressure while applying a current such that thesolenoid valve forms a target pressure (a temporary VKP: a secondreference pressure), then maintaining the current for the time forforming the target pressure, and then increasing the current again, asdescribed above.

When the temporary VKP is similar to the actual VKP, the measuredhydraulic pressure passes through the nonlinear section as the currentincreases, so that the pressure drop may occur.

However, when the pressure drop does not occur, it may be interpreted asmeaning that the temporary VKP is inappropriate.

According to the above-described purpose, the second reference pressuremay also be set to a level that makes it possible to determine whetherthe current temporary VKP is similar to the actual VKP, and may be setto, for example, 0.5 bar or the like.

Accordingly, when the pressure drop occurs in the state in which thesolenoid valve is made to form the pressure obtained by adding thepredetermined first reference pressure to the temporary VKP or when thepressure drop does not occur in the state in which the solenoid valve ismade to form the pressure obtained by subtracting the predeterminedsecond reference pressure from the temporary VKP, it is possible to morecorrectly set the temporary VKP by repeating the setting of thetemporary VKP and the accumulating of the number of times of setting thetemporary VKP.

The setting of the temporary VKP and the accumulating of the number oftimes of setting the temporary VKP may be repeated together with thegenerating of the current-hydraulic pressure model.

That is, as illustrated in FIG. 2 and FIG. 3, a current sweep isperformed to gradually increase the current applied to the solenoidvalve to obtain the slope of the measured hydraulic pressure to generatea current-hydraulic model, then a current sweep is performed again, andthe entire process of setting the temporary VKP using the differencebetween the model hydraulic pressure based on a model-hydraulic pressuremodel and the measured hydraulic pressure is repeated.

Of course, it may also be possible to set the temporary VKP by obtainingagain the measured hydraulic pressure by sweeping the current and usingthe current-hydraulic model generated in the previous process whileomitting the generating of the current-hydraulic model.

When the number of times of setting the temporary VKP is a predeterminedfirst reference number, among temporary VKPs that have been set untilthe first reference number is reached, an average value of remainingtemporary VKPs excluding a maximum value and a minimum value is set asthe final VKP.

When the number of times of setting the temporary VKP has reached to thefirst number of times, it means that an appropriate pressure dropoperation has not been determined although the processes of setting thetemporary VKP, determining the pressure drop in the state of the targetpressure according to the first reference pressure, and determining thepressure drop in the state of the target pressure according to thesecond reference pressure were repeated multiple times. Thus, it isdetermined that it is a situation in which the setting of an appropriateVKP is difficult under the determination using the pressure drop due tothe influence of the sticking phenomenon of the solenoid valve or thelike, and the average value of the temporary VKPs, which have been setso far, is set as the final VKP.

In the instant case, the maximum and minimum values are excluded fromthe temporary VKPs, which have been set so far to avoid the influence ofnoise as much as possible.

Therefore, the first reference number of times is set to a degree thatmakes it possible to determine whether it is difficult to set anappropriate VKP based on the determination made using the pressure dropanymore according to the above-described purpose. The first referencenumber of times may be determined by design through a number of testsand analysis, and may be set to, for example, five times or the like.

Meanwhile, in the determining of the pressure drop in the state in whichthe solenoid valve forms a fourth reference pressure obtained bysubtracting a predetermined third reference pressure from the temporaryVKP, and determining whether the pressure drop is within a predeterminedreference range, the controller is configured to apply a current to forma target pressure (the fourth reference pressure) to the solenoid valve,as described above, and after the time for forming the target pressuretime elapses, the controller is configured to determine whether thepressure drop appropriately occurs by observing the state in which themeasured hydraulic pressure follows the increase of the model hydraulicpressure while increasing the current again.

Here, the reference range of the pressure drop may be set by adding alittle margin up and down with reference to the pressure drop obtainedby integrating the difference between the model hydraulic pressure andthe measured hydraulic pressure while increasing the current again afterthe time for forming the target pressure in the state in which a currentcorresponding to the actual VKP is applied to the solenoid, and may bedetermined by design by performing the tests described above multipletimes in advance.

That is, the reference range of the pressure drop is set such that it ispossible to determine whether the currently set temporary VKP issufficiently close to the actual VKP, and to determine whether thecandidate VKP may be set as the final VKP.

For reference, when the pressure drop is obtained in the state in whicha current corresponding to an actual VKP is applied to the solenoidvalve, the measured hydraulic pressure forms a slightly nonlinearsection and then a linear section, and thus it is normal that a slightpressure drop occurs accordingly. When the pressure drop is within thepredetermined reference range, it means that the pressure drop occurs atthe level described above.

Here, the third reference pressure is set such that, even if the currenttemporary VKP is the same as the actual VKP, the pressure drop which issubstantially generated in a process of determining whether a pressuredrop occurs as described above can exceed the reference range.

This is due to the following reason: when it is determined that thepressure drop obtained using the fourth reference pressure obtained bysubtracting the third reference pressure from the temporary VKP as atarget pressure exceeds the reference range and then the pressure dropobtained while updating the fourth reference pressure (a targetpressure) to be described later gradually converges to a value withinthe above reference range, it is possible to consider that the fourthreference pressure gradually approaches the actual VKP while beingupdated, and ultimately, it is possible to set a more accurate VKP.

Accordingly, according to the above-described purpose, even if thetemporary VKP is the same as the actual VKP, it is desirable to set thethird reference pressure to a level at which the pressure drop obtainedusing, as a target pressure, a fourth reference pressure obtained bysubtracting the third reference pressure from the temporary VKP exceedsthe reference range. The third reference pressure may be determined bydesign through a number of tests and analysis, and may be set to, forexample, 0.5 bar.

The method may further include updating the fourth reference pressure asa pressure obtained by subtracting a predetermined fifth referencepressure from the fourth reference pressure when the pressure drop issmaller than the reference range as a result of determining the pressuredrop in the state in which the solenoid valve is set the fourthreference pressure, wherein the determining of the pressure drop isrepeated in a state in which the solenoid valve is made to form theupdated fourth reference pressure.

Furthermore, the method may further include updating the fourthreference pressure as a pressure obtained by adding a predeterminedsixth reference pressure to the fourth reference pressure when thepressure drop is greater than the reference range as a result ofdetermining the pressure drop in the state in which the solenoid valveis set the fourth reference pressure, wherein the determining of thepressure drop is repeated in a state in which the solenoid valve is madeto form the updated fourth reference pressure.

That is, from the state in which the pressure drop obtained using, as atarget pressure, the fourth reference pressure obtained by subtractingthe third reference pressure from the temporary VKP is made to exceedthe reference range, the fourth reference pressure close to the actualVKP is found by increasing the fourth reference pressure (targetpressure) by the sixth reference pressure such that the pressure dropconverges to a value within the reference range, as described above.

However, when the pressure drop obtained using, as a target pressure,the fourth reference pressure obtained by subtracting the thirdreference pressure from the temporary VKP does not reach the referencerange, the fourth reference pressure close to the actual VKP is found bydecreasing the fourth reference pressure (target pressure) by the fifthreference pressure such that the pressure drop converges to a valuewithin the reference range.

Therefore, according to the above-described purpose, to make the fourthreference pressure converge to the actual VKP, it is desirable toappropriately set the fifth reference pressure and the sixth referencepressure through a plurality of tests and analysis such that the fifthreference pressure and the sixth pressure can relatively accuratelyconverge to the actual VKP without repeating the above-describedprocesses too long. For example, the fifth reference pressure and thesixth reference pressure may be set to 0.1 bar or the like.

Of course, the fifth reference pressure and the sixth reference pressuremay be set equal to each other, but may be set to different values.

As the fourth reference pressure is gradually updated as describedabove, when it is determined that the pressure drop obtained using thefourth reference pressure as the target pressure falls within thereference range, the fourth reference pressure at that time is stored asa candidate VKP, the pressure drop is obtained again using the fourthreference pressure as a target pressure, it is determined whether thepressure drop falls within the reference range, and the process ofstoring the fourth reference pressure at that time as the candidate VKPis repeated.

When the number of times of storing the fourth reference pressure of thesame value as the candidate VKP reaches the second reference number oftimes by repeating the above process, it may be assured that thecandidate VKP at the instant time is substantially the same as theactual VKP. Thus, the candidate VKP is stored as the final VKP, and thenthe controller controls the clutch using the final VKP.

Accordingly, according to the above-described purpose, the secondreference number of times is set to a level that makes it possible todetermine that it is appropriate to set the candidate VKP as the finalVKP, and may be set to, for example, five times or the like.

Furthermore, the term related to a control device such as “controller”,“control unit”, “control device” or “control module”, etc refers to ahardware device including a memory and a processor configured to executeone or more steps interpreted as an algorithm structure. The memorystores algorithm steps, and the processor executes the algorithm stepsto perform one or more processes of a method in accordance with variousexemplary embodiments of the present invention. The control deviceaccording to exemplary embodiments of the present invention may beimplemented through a nonvolatile memory configured to store algorithmsfor controlling operation of various components of a vehicle or dataabout software commands for executing the algorithms, and a processorconfigured to perform operation to be described above using the datastored in the memory. The memory and the processor may be individualchips. Alternatively, the memory and the processor may be integrated ina single chip. The processor may be implemented as one or moreprocessors. The processor may include various logic circuits andoperation circuits, may process data according to a program providedfrom the memory, and may generate a control signal according to theprocessing result.

The control device may be at least one microprocessor operated by apredetermined program which may include a series of commands forcarrying out the method disclosed in the aforementioned variousexemplary embodiments of the present invention.

The aforementioned invention can also be embodied as computer readablecodes on a computer readable recording medium. The computer readablerecording medium is any data storage device that can store data whichmay be thereafter read by a computer system. Examples of the computerreadable recording medium include hard disk drive (HDD), solid statedisk (SSD), silicon disk drive (SDD), read-only memory (ROM),random-access memory (RAM), CD-ROMs, magnetic tapes, floppy discs,optical data storage devices, etc and implementation as carrier waves(e.g., transmission over the Internet).

In various exemplary embodiments of the present invention, eachoperation described above may be performed by a control device, and thecontrol device may be configured by a plurality of control devices, oran integrated single control device.

In various exemplary embodiments of the present invention, the controldevice may be implemented in a form of hardware or software, or may beimplemented in a combination of hardware and software.

For convenience in explanation and accurate definition in the appendedclaims, the terms “upper”, “lower”, “inner”, “outer”, “up”, “down”,“upwards”, “downwards”, “front”, “rear”, “back”, “inside”, “outside”,“inwardly”, “outwardly”, “interior”, “exterior”, “internal”, “external”,“forwards”, and “backwards” are used to describe features of theexemplary embodiments with reference to the positions of such featuresas displayed in the figures. It will be further understood that the term“connect” or its derivatives refer both to direct and indirectconnection.

Furthermore, the term of “fixedly connected” signifies that fixedlyconnected members always rotate at a same speed. Furthermore, the termof “selectively connectable” signifies “selectively connectable membersrotate separately when the selectively connectable members are notengaged to each other, rotate at a same speed when the selectivelyconnectable members are engaged to each other, and are stationary whenat least one of the selectively connectable members is a stationarymember and remaining selectively connectable members are engaged to thestationary member”.

The foregoing descriptions of specific exemplary embodiments of thepresent invention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit thepresent invention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteachings. The exemplary embodiments were chosen and described toexplain certain principles of the present invention and their practicalapplication, to enable others skilled in the art to make and utilizevarious exemplary embodiments of the present invention, as well asvarious alternatives and modifications thereof. It is intended that thescope of the present invention be defined by the Claims appended heretoand their equivalents.

What is claimed is:
 1. A method of setting a clutch control referencevalue, the method comprising: generating, by a controller, acurrent-hydraulic model using a slope of a measured hydraulic pressureobtained by measuring a hydraulic pressure acting on a clutch whilechanging a current applied by the controller to a solenoid valveelectrically connected to the controller and fluidically connected tothe clutch; setting, by the controller, a current at which a differencebetween a model hydraulic pressure determined according to thecurrent-hydraulic pressure model and the measured hydraulic pressure ismaximum, as a temporary volumetric kiss point (VKP) while changing thecurrent applied to the solenoid valve, and accumulating, by thecontroller, a number of times of setting the temporary VKP; determining,by the controller, whether a predetermined pressure drop occurs in astate in which the solenoid valve is made to form a pressure obtained byadding a predetermined first reference pressure to the temporary VKP;determining, by the controller, whether the predetermined pressure dropoccurs in a state in which the solenoid valve is made to form a pressureobtained by subtracting a predetermined second reference pressure fromthe temporary VKP; making, by the controller, the solenoid valve form afourth reference pressure obtained by subtracting a predetermined thirdreference pressure from the temporary VKP upon determining that thepressure drop does not occur in a state in which the solenoid valve ismade to form the pressure obtained by adding the predetermined firstreference pressure to the temporary VKP and upon determining that thepressure drop occurs in a state in which the solenoid valve is made toform the pressure obtained by subtracting the predetermined secondreference pressure from the temporary VKP; determining, by thecontroller, the pressure drop in a state in which the solenoid valveforms the fourth reference pressure and determining, by the controller,whether the pressure drop is within a predetermined reference range;storing, by the controller, the fourth reference pressure as a candidateVKP upon determining that the pressure drop is within the predeterminedreference range, and accumulating, by the controller, a number of timesof storing the same fourth reference pressure as the candidate VKP;determining, by the controller, whether the pressure drop is within thepredetermined reference range and repeating, by the controller, thestoring of the fourth reference pressure as the candidate VKP and thesetting of the candidate VKP as a final VKP upon determining that thenumber of times of storing the same fourth reference pressure as thecandidate VKP becomes a predetermined first reference number of times;and controlling, by the controller, the solenoid valve using the finalVKP.
 2. The method of claim 1, further including: repeating, by thecontroller, the setting of the temporary VKP and the accumulating of thenumber of times of setting the temporary VKP, upon determining that thepressure drop occurs in the state in which the solenoid valve is made toform the pressure obtained by adding the predetermined first referencepressure to the temporary VKP or upon determining that the pressure dropdoes not occur in the state in which the solenoid valve is made to formthe pressure obtained by subtracting the predetermined second referencepressure from the temporary VKP.
 3. The method of claim 2, wherein thesetting of the temporary VKP and the accumulating of the number of timesof setting the temporary VKP are repeated with the generating of thecurrent-hydraulic pressure model.
 4. The method of claim 1, furtherincluding: setting, by the controller, an average value of temporaryVKPs that have been set until a predetermined second reference number isreached, as the final VKP, upon determining that the number of times ofsetting the temporary VKP is the predetermined second reference number.5. The method of claim 4, wherein in setting the average value,remaining temporary VKPs excluding a maximum value and a minimum valueamong the temporary VKPs is set as the final VKP.
 6. The method of claim1, further including: updating, by the controller, the fourth referencepressure as a pressure obtained by subtracting a predetermined fifthreference pressure from the fourth reference pressure upon determiningthat the pressure drop is smaller than the reference range as a resultof determining the pressure drop in the state in which the solenoidvalve is set the fourth reference pressure.
 7. The method of claim 6,wherein the determining of the pressure drop is repeated in a state inwhich the solenoid valve is made to form the updated fourth referencepressure.
 8. The method of claim 1, further including: updating, by thecontroller, the fourth reference pressure as a pressure obtained byadding a predetermined sixth reference pressure to the fourth referencepressure upon determining that the pressure drop is greater than thereference range as a result of determining the pressure drop in thestate in which the solenoid valve is set the fourth reference pressure.9. The method of claim 8, wherein the determining of the pressure dropis repeated in a state in which the solenoid valve is made to form theupdated fourth reference pressure.
 10. A non-transitory computerreadable storage medium on which a program for performing the method ofclaim 1 is recorded.
 11. A clutch apparatus for setting a clutch controlreference value, the clutch apparatus comprising: a clutch; a solenoidvalve fluidically connected to the clutch; and a controller electricallyconnected to the solenoid valve, wherein the controller is configuredfor: generating a current-hydraulic model using a slope of a measuredhydraulic pressure obtained by measuring a hydraulic pressure acting onthe clutch while changing a current applied by the controller to thesolenoid valve; setting a current at which a difference between a modelhydraulic pressure determined according to the current-hydraulicpressure model and the measured hydraulic pressure is maximum as atemporary volumetric kiss point (VKP) while changing the current appliedto the solenoid valve, and accumulating a number of times of setting thetemporary VKP; determining whether a predetermined pressure drop occursin a state in which the solenoid valve is made to form a pressureobtained by adding a predetermined first reference pressure to thetemporary VKP; determining whether the predetermined pressure dropoccurs in a state in which the solenoid valve is made to form a pressureobtained by subtracting a predetermined second reference pressure fromthe temporary VKP; making the solenoid valve form a fourth referencepressure obtained by subtracting a predetermined third referencepressure from the temporary VKP upon determining that the pressure dropdoes not occur in a state in which the solenoid valve is made to formthe pressure obtained by adding the predetermined first referencepressure to the temporary VKP and upon determining that the pressuredrop occurs in a state in which the solenoid valve is made to form thepressure obtained by subtracting the predetermined second referencepressure from the temporary VKP; determining, the pressure drop in astate in which the solenoid valve forms the fourth reference pressureand determining, by the controller, whether the pressure drop is withina predetermined reference range; storing the fourth reference pressureas a candidate VKP upon determining that the pressure drop is within thepredetermined reference range, and accumulating, by the controller, anumber of times of storing the same fourth reference pressure as thecandidate VKP; determining whether the pressure drop is within thepredetermined reference range and repeating, by the controller, thestoring of the fourth reference pressure as the candidate VKP and thesetting of the candidate VKP as a final VKP upon determining that thenumber of times of storing the same fourth reference pressure as thecandidate VKP becomes a predetermined first reference number of times;and controlling the solenoid valve using the final VKP.
 12. The clutchapparatus of claim 11, wherein the controller is further configured for:repeating the setting of the temporary VKP and the accumulating of thenumber of times of setting the temporary VKP, upon determining that thepressure drop occurs in the state in which the solenoid valve is made toform the pressure obtained by adding the predetermined first referencepressure to the temporary VKP or upon determining that the pressure dropdoes not occur in the state in which the solenoid valve is made to formthe pressure obtained by subtracting the predetermined second referencepressure from the temporary VKP.
 13. The clutch apparatus of claim 12,wherein the setting of the temporary VKP and the accumulating of thenumber of times of setting the temporary VKP are repeated with thegenerating of the current-hydraulic pressure model.
 14. The clutchapparatus of claim 11, wherein the controller is further configured for:setting an average value of temporary VKPs that have been set until apredetermined second reference number is reached, as the final VKP, upondetermining that the number of times of setting the temporary VKP is thepredetermined second reference number.
 15. The clutch apparatus of claim14, wherein in setting the average value, remaining temporary VKPsexcluding a maximum value and a minimum value among the temporary VKPsis set as the final VKP.
 16. The clutch apparatus of claim 11, whereinthe controller is further configured for: updating the fourth referencepressure as a pressure obtained by subtracting a predetermined fifthreference pressure from the fourth reference pressure upon determiningthat the pressure drop is smaller than the reference range as a resultof determining the pressure drop in the state in which the solenoidvalve is set the fourth reference pressure.
 17. The clutch apparatus ofclaim 16, wherein the determining of the pressure drop is repeated in astate in which the solenoid valve is made to form the updated fourthreference pressure.
 18. The clutch apparatus of claim 11, wherein thecontroller is further configured for: updating the fourth referencepressure as a pressure obtained by adding a predetermined sixthreference pressure to the fourth reference pressure upon determiningthat the pressure drop is greater than the reference range as a resultof determining the pressure drop in the state in which the solenoidvalve is set the fourth reference pressure.
 19. The clutch apparatus ofclaim 18, wherein the determining of the pressure drop is repeated in astate in which the solenoid valve is made to form the updated fourthreference pressure.